The best capper I have ever used on tip-up/break action/drop block/swing block type actions is this one that T/C used to make. I don't know why but it seems they have discontinued this one a couple years ago.
It is made for 209's, but works equally well with the .25 ACP too. I just call it the injectomatic.
If you can still find one, it will be worth the effort.